Light Scattering Grade Barium Sulfate
SHANGHAI, March 3, 2014 /PRNewswire/ — Shanghai U-times Chemical Technology Co., LTD was established in 2005, and has always focused on R&D and supply of the raw materials and additives in high-end plastic industries. Since 2008, we have paid more attention to the environmentally friendly material “barium sulfate,” and have continually launched several grades of functional barium sulfate to be used in different kinds of plastics for different functions, especially in the LED industry for light scattering.
People in today’s world cannot leave LED. With the development of the LED industry, its standard level goes much higher, and the requirements of light design becomes much stricter. For example, the effectiveness of the heat radiation of the lights becomes better, while the thickness of the light covers becomes thinner. The haze of the lights needs to be maintained, while the light transmittance needs to be higher. Definitely, we cannot do all the work or solve all the problems. However, we have concentrated on the problems of “how to increase the light scattering effectiveness while keeping the haze and transmittance.”
First, let’s come to the “light scattering materials.” Actually, light scattering material is the key point of the LED optical design — much more important than the chip and driver. As everybody knows, LED is point source light, which is quite glaring and cannot be used in direct lighting. That’s’ why we need the LED light to go through a high quality scattering material, and make the light scattered. However, if you use a low quality scattering material, the light transmittance is also low and you’ll waste a lot of luminous energy. In the old days, the light transmittance efficiency was only about 40%, while now it has reached 80%.
Usually, light scattering material is made of three parts: transparent material, scattering additives, and molding. As for transparent materials, there are PC, PMMA, PS, etc., which are used more often today. As for the scattering additives, we can separate them into two categories. One is organic, and the other is inorganic. People may know more about the organic scattering additives, such as the Silanes, which can increase the haze with only a little addition. But its disadvantages are also the problems, e.g., the high cost, poor temperature/light/chemical resistance, etc. The longer you use it, the more the optical performance degrades.
As to the inorganic scattering additives, barium sulfate is preferred. The reason is barium sulfate is almost inert to everything, so the chemical resistance is much better. Thanks to its high transparency, it can increase the transmittance efficiency while keeping the haze. However, it doesn’t mean all kinds of barium sulfate can be used as scattering additives. It must be cubic with a big particle size, and having a closer particles distribution can also help a lot. The reason is that the cubic ones have six sides, and one beam of light going in through one side will be scattered into five beams of light going out through the other five sides. Spherical crystal is different, because it has no sides and no angels to refract the light going in and scattering it. Put simply, crystals with more sides will have the scattering performance, and only cubic crystals will have regular scattering performance.
If the haze is the same, the scattering materials modified by cubic barium sulfate will have better light transmittance and scattering efficiency.
People may ask if barium sulfate can be used as the scattering additive, how about natural barite? The answer is no. Natural barites contain a lot of impurities, like metals, which will change performance. Also, the irregular shapes don’t have the scattering effect.
Anyway, the cost of barium sulfate is much lower than organic additives.
The LED industry is fast improving, and we believe only the fittest will survive.
SOURCE Shanghai U-times Chemical Technology Co., Ltd